Field of the Invention
The invention relates to a device for applying powder to sheets passing sequentially through a printing press in a conveying direction along a conveyor route, the sheets being combinable into a sheet pile in a manner that one respective side of the upper and rear sides of a respectively following sheet is situated opposite the other respective side of the upper and rear sides of a respectively preceding sheet, after powder has been applied thereto through the intermediary of a powder-bearing gas curtain associated with the conveyor route and formed of a carrier gas conveying powder particles therewith, and further relates to such a powder-applying device in combination with a delivery of a sheet-processing printing press.
Heretofore known devices for applying powder to sheets have a powder-bearing gas dispensing device, such as a sprayer, which produces a powder-bearing gas curtain directed against the upper side of the sheets. This upper side is the front or recto side in the case of sheets which are printed on only one side thereof. The powder-bearing gas is made-ready in or supplied to the powder-bearing gas dispensing or sprayer device by a powder-bearing gas generator which distributes powder particles in a carrier-gas flow. By applying powder to the sheets, the latter are prevented from being baked together if a coating thereon of printing ink or varnish has not yet hardened completely when the sheets have been laid upon one another on a sheet pile.
In the heretofore known conventional devices, the powder-bearing gas dispensing or spraying device must be arranged at a relatively great distance from the conveyor route of the sheets in order that the grippers moving the sheets can run through unhindered between the sheets and the powder-bearing gas dispensing device. For this reason, the transfer of powder onto the sheets is not always satisfactory.